It's one and done usually.Can you re-use the mixture to do a second tank, or is it one and done?
Thanks for the link!
Unless the (steel) tank is pitted or has flaky scaly rust and need major refurbishing there is no need to use media/tumble. And definitely no need to screw around with whips and then washing out the rust dust.
Phosphoric acid removes all rust, getting the concentration right is the only issue - more is not always better. Phosphoric acid is food grade (its in coke and pepsi), the same acid in "naval jelly" and there is no residue to worry over O2 wise. You still need to rinse it out in order to heat up the tank enough to be able to dry it.